Gardai are encountering a 'wall of silence' over the fatal stabbing of a 'respectable young man' by a teenage associate of the former gang figure Freddie Thompson.

Lorcan O'Reilly, 21, died after being stabbed in the chest as he tried to prevent another young man being attacked at the Oliver Bond flats, near the Guinness brewery in Dublin, on Halloween night.

The main suspect, who was 14 at the time and has since turned 15, was captured on CCTV security cameras, as were up to 15 young men and women.

However, of the nine people so far questioned by gardai, none has been prepared to give a witness statement.

Under normal circumstances, the case would be straightforward, given the amount of witnesses and the CCTV images, which would provide strong corroborative evidence but would not be enough for a successful prosecution.

It is believed that the reticence of witnesses is due to intimidation by Thompson's few remaining associates in the south inner city.

Price on his head: Freddie Thompson is now in hiding

Thompson, 34, fled Ireland after being released from prison in August, having served a 14-month sentence for assault relating to a pub brawl in January 2013.

Gardai believe that Thompson has been placed on an assassination list by the major Irish drugs cartel, headed by Christy Kinahan, 57, and based in southern Spain, which has accused the once-notorious Dublin gang leader of giving information to Spanish police.

Thompson has been living with a woman of Irish background in north London since his release from prison.

Local sources in the south inner city said Thompson cannot return to Dublin for fear of assassination.

He has found himself in the same position as John Gilligan, 63, who was shot and seriously injured in the third attempt on his life within three months of being released from prison in October 2013. He too fled to England, where he remains in hiding for fear of assassination by the Irish drugs cartel.

A source in south inner Dublin told the Sunday Independent that Thompson's former associates have been issuing threats to potential witnesses to the stabbing of Lorcan O'Reilly, who had never come to the gardai's notice and is described as having been a "respectable young man from a respectable family".

It is believed that Mr O'Reilly was socialising with friends when the teenage suspect deliberately began a row with one of his friends.

The teenager left the scene and collected a kitchen knife with which he attempted to stab his intended victim.

However, Mr O'Reilly tried to intervene and suffered a stab wound to his chest that is understood to have severed his aorta. The incident happened at around 2.45am. Mr O'Reilly was taken to the nearby Mater Hospital but was later pronounced dead.

Local people have said that there is widespread disgust over both the killing and the threats to witnesses. They said that the criminal figures involved are themselves effectively under threat from the Kinahan gang in Dublin and are not in a position to carry out any of the threats against any of the witnesses.

Freddie Thompson was extradited to Spain on foot of a warrant from police in October 2011, six months after a series of major raids against the Kinahan empire, in which Spanish authorities said they seized up to €500m worth of property and cash.

Thompson was initially imprisoned in Spain but released shortly afterwards.

He returned to Dublin over Christmas 2012 and was involved in the vicious brawl in a pub in the Liberties area which led to his imprisonment. He fled to England hours after his release.